Anything below 72 or 7p degrees but I run my reservoirs at 65 to 68Yeah no cover we made one big one so its easier to clean out, should I be using a cover? I also have a 100 gallon in the back room I used to use (http://www.globalindustrial.com/p/storage/bins-totes-containers/stocktanks/rubbermaid-fg424288bla-stock-tank-100-gallon-black-270079?infoParam.campaignId=T9F&gclid=CjwKEAjwltC9BRDRvMfD2N66nlISJACq8591ts8_XH-GwmHn-FLd0DJZikFCM4GemFOEyH7nadX8QxoCO-fw_wcB)
We are going to be using a chiller aren't you suppose to with hydroponics and do you know what tempature the water should be chilled to?